とめる【留める】
1. 〔固定する, 押さえる〕fix, secure, anchor, fasten, retain, lock, hold (down); 〔(各種の留め具で)留める〕screw (down), clamp, clasp, latch, tie down, tie up, tack, staple, bolt, nail, rivet, pin, clip, buckle, button, snap, hook (up), glue; 〔留め置く〕trap, lodge
◆the Velcro-fastened edges of the fabric マジックテープで留めてあるその布地の端
◆a cable retaining bolt ケーブル留めボルト
◆a Velcro-secured flap マジックテープで留めてある[マジックテープ式]フラップ
◆Remove the bolts that hold A to B. AをBに留めているボルトを取り外してください.

とめ【止め, 留め】
◆a stop valve 止め弁
◆a set screw 止めねじ
◆a locking nut 止めナット
◆tighten the impeller retaining nut インペラ止めナットを締める
　
ビジネス技術実用英語大辞典　第３版

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Note added at 29 mins (2010-10-15 05:25:42 GMT)
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追加：number of tightening

See: http://books.google.co.th/books?id=Yn9F0RhJ0EkC&pg=PA648&lpg... and http://books.google.co.th/books?id=Yn9F0RhJ0EkC&pg=PA648&lpg...

--- This could be referring to the number of turns required to tighten/secure the screw. Please see websites below - some mention the precise number of turns necessary to tighten a screw.

http://www.750ace.com/task_31.phtml?CLmDemo_horizontal=5
You will now see the small pilot screw under where the plug was. Take a small flat screwdriver and gently turn the pilot screw IN (clockwise) until it seats, counting the number of turns it takes. Use gentle force as this screw is very thin and has O-ring seals on it.

Now turn the screw OUT (counter-clockwise) the number of turns in the table below.

http://www.stangnet.com/mustang-forums/609695-where-iac-air-...
Tighten screw exactly 1 1/2 turns. If the screw is very loose, put a drop of loc-tite or silicone on it, so it doesn't work out of adjustment.



1. Pipeline rules of thumb handbook: quick and accurate solutions to ... - Google Books Result
E. W. McAllister - 2009 - Technology & Engineering - 747 pages
The greater the number of screw turns is, the longer the screw (screw length equals the number of turns multiplied by the screw pitch) is. ...
books.google.com/books?isbn=1856175006...

1. [PDF]
transmission servicing at.pdf - Article Print
File Format: PDF/Adobe Acrobat - Quick View
2) Tighten screw to 41 INCH lbs. (4.6 N.m) and back off screw at indicated number of turns. See LOW-REVERSE (REAR) BAND. ADJUSTMENT table. ...
jeepgarage.free.fr/.../transmission%20servicing%20at.pdf - Similar

In general usage, this appears to mean simply the number of screws. Thus if not all the screws are used, the remaining screws are more liable to work loose than if all the screws are used.

One example is in the last line of the penultimate paragraph on the following page:
http://www.g-mark.org/award/detail.html?id=31311&sheet=detai...

The following patent has a slight complication in that it mentions both ビス止め点数 and ビス止め数 in the same sentence. In this particular example ビス止め点数 would be something like the "number of screw fixing points", while ビス止め数 would be the "number of screws" or the "number of screw fixings".

ビス止め点数を減らして代わりにコ字状部を有する止め金を使用し、取付け作業を簡単にし且つビス止め数を減らした液晶表示装置を提供する。

http://www.ekouhou.net/液晶表示装置/disp-A,2007-171484.html

I would suggest that in the translation in question here, the "number of screws" would cover the meaning adequately.

”止め”　in screw parlance refers to set screws so 止め点数　likely refers to the set screw(s) and the possibility of loosness of one or more of the set screws in the assembly. Checking all the set screws to determine if one or more is loose in likely intended here.